When we talk about priority areas, we generally mean the sectors that have received the highest allocations (most money). This is one way of understanding choices and relative priorities.
However, not all areas are equally expensive. For example, if one consideres international benchmarking for different sectors, education is usually more expensive than health, health more expensive than agriculture, and agriculture more expensive than water.
It does not follow that spending more on health than water means health is more a priority than water.